Conventionally, an orthodontic treatment is carried out by retaining an archwire on an attachment such as a bracket or a tube mounted on teeth and transmitting the restoring force of the archwire to the teeth. Therefore, in order to retain the archwire within an archwire slot formed in the bracket, generally, there is used, for example, an elastomeric ring made of synthetic resin such as urethane resin or silicone resin, or a connecting wire such as a ligature wire made of metal, which can be caught on tie wings of the bracket for retaining the archwire.
However, the elastomeric ring, due to the property of its material, under the intraoral environment, deteriorates and loses its elasticity or is easy to break, so that it must be replaced frequently. Consequently, it has become a large burden to a patient and a doctor.
On the other hand, in the case of the ligature wire, since it is made of metal, the degree of ligation is hard to decide. That is, when it is ligated too tight, frictional resistance between the archwire and archwire slot increases to fail to obtain a desired correcting force, which causes the extended treatment period. Further, there is a fear that the cut end of the wire can damage the oral mucosa of a patient.
Thus, in order to solve the above problems, there has been demanded a ligating tool which can be easily mounted onto and removed from a bracket, can reduce its frictional resistance with respect to an archwire and can provide an aesthetic appearance.
In view of the above circumstances, there is proposed a ligating sheet made of elastic material which can cover the entire surface of the bracket and ligate the archwire to thereby reduce its frictional resistance with respect to the archwire and thus move the teeth smoothly (see, for example, the patent reference 1).
There is also known an orthodontic bracket cap (for example, see the patent reference 2, 3 and 4) made of elastic material having a color approximate to the teeth color which, similarly to the above reference 1, while covering the entire surface of the bracket, ligates the archwire and also includes a hook for mounting an auxiliary wire and a fitting portion to be fitted with the bracket.
On the other hand, there is further known a cross-shaped ligating tool which can be used while it is engaged between the archwire slot and mesiodistal tie wings (for example, see the patent reference 5).